Sheets of retinal pigmented epithelium (RPE), isolated at several developmental stages from the eyes of chick embryos, gave rise in tissue cultures to patches of differentiating neural retina. These metaplastic foci arise toward the centers of the explants. The steps identified in their appearance were: local depigmentation of the RPE sheet, first detected after three days in culture; rapid mitosis in the depigmented regions; stratification of the nuclei within these foci; and differentiation of the major layers characteristic of neural retina (NR). RPE from donors younger than developmental stage 27 gave rise to patches of NR, those from older donors did not. The polarity of metaplastic foci of NR was concordant with that of the RPE in which they arose.